Optical fiber arrays

ABSTRACT

An optical fiber array ( 20,40 ) comprising at least one subunit ( 26,46 ) including at least one optical fiber ( 22 ) therein surrounded by a respective subunit matrix ( 23,43 ) having a subunit matrix modulus characteristic. The optical fiber array ( 20,40 ) includes a common matrix ( 24,44 ) disposed adjacent to the at least one subunit ( 26,46 ) and having a common matrix modulus characteristic. A subunit/common matrix modulus ratio being defined as a ratio of the subunit matrix modulus characteristic with respect to the common matrix modulus characteristic, the subunit/common matrix modulus ratio being greater than about 1.5:1. The optical fiber array ( 20,40 ) can include an adhesion zone ( 28,48 ) defining a controlled adhesion bond between the common and subunit matrices ( 24,26;44,46 ).

The present invention relates to arrays of optical fibers and, moreparticularly, to optical fiber ribbons.

GENERAL CONSTRUCTION OF AN OPTICAL FIBER RIBBON

Optical fiber ribbons are used to transmit telecommunication, computer,and data information. The general structure of an optical fiber ribbon,and the materials and processing variables applied in the manufacture ofan optical fiber ribbon can play a significant role in how an opticalfiber ribbon will perform in the field. Optical fiber ribbon structurescan be generally classified into two general categories, namely, ribbonswithout subunits and ribbons including subunits. A ribbon/subunit designtypically includes a subunit with at least one optical fiber surroundedby a subunit matrix that, in turn, is surrounded by a common matrix thatalso surrounds at least one other subunit.

An optical fiber ribbon without subunits can present problems for thecraft. For example, when separating optical fiber ribbons that do notcontain subunits into optical fiber subsets, the craft must useexpensive precision tools. Moreover, connectorization/splice procedurescan require inventories of specialized splice and closure units/toolsfor the various subsets of optical fibers. Where the craft elects toseparate the optical fiber ribbon into subsets by hand, or with a toollacking adequate precision, stray optical fibers can result. Strayoptical fibers can cause problems in optical ribbon connectorization,organization, stripping, and splicing.

An exemplary optical fiber ribbon 1 is shown in FIG. 1. Optical fiberribbon 1 includes subunits 2 having optical fibers 3 disposed in asubunit matrix 5 and surrounded by a common matrix 4. Optical fiberribbons having subunits can have several advantages, for example,improved separation, and avoidance of stray fiber occurrences.Additionally, optical fiber ribbons having subunits can result in areduction of the overall cable diameter so that high fiber-densitynetworks can be achieved. However, one handling concern is the potentialformation of wings W (FIG. 1) during hand separation of the subunits.This can be caused by a lack of sufficient adhesion between commonmatrix 4 and subunit matrix 5. The existence of wings W can negativelyaffect, for example, optical ribbon organization, connectorization,stripping, and splicing operations by the craft. Additionally, wings Wcan cause problems with ribbon identification markings, or compatibilityof the subunit with ribbon handling tools, for example, thermalstrippers, splice chucks, and fusion splicers.

UV Materials in Ribbon Construction

Organic materials of the ultra-violet light curable (UV curable) type,and visible light curable type, have been developed for use as a baseresin for subunit and common matrices. UV curable materials aregenerally tough, exhibit high resistance to abrasion, perform well whenunder stress, and are adaptable to mass production processes. Whencured, a UV curable subunit matrix typically has a modulus of about 10⁶Pa, and a UV curable common matrix should have a relatively highermodulus of about 10⁹ Pa.

Review of UV Curing Process in Ribbon Manufacture

The curing of a UV radiation-curable composition suitable for use as asubunit or common matrix material is essentially a polymerization of theUV curable material, whereby the material undergoes a transition from aliquid to a solid. Prior to application to an optical fiber or asubunit, the UV curable material comprises a mixture of formulations ofliquid monomers, oligomer “backbones” with, e.g., acrylate functionalgroups, photoinitiators, and other additives. Photoinitiators functionby: absorbing energy radiated by the UV or visible light source;fragmenting into reactive species; and then initiating apolymerization/hardening reaction of the monomers and oligomers. Theresult is, in general, a solid network of crosslinking between themonomers and oligomers that may include fugitive components after cure.The photoinitiator therefore begins a chemical reaction, that promotesthe solidification of the liquid matrix to form a generally solid filmhaving modulus characteristics.

A key to the curing process is the reaction of a photoinitiator inresponse to UV radiation. A photoinitiator has an inherent absorptionspectrum that is conveniently measured in terms of absorbance as afunction of the wavelength of the radiated light. Each photoinitiatorhas a characteristic photoactive region, i.e., a photoactive wavelengthrange (typically measured in nanometers (nm)). Commercially availablephotoinitiators may have a photoactive region in the vacuum ultra-violet(VuW) (160-220 nm), ultra-violet (UV) (220-400 nm), or visible light(V-light)(400-700 nm) wavelength range. When the material is irradiatedby a VUV, UV or V-light lamp, that emits light in the photoactiveregion, the material will cure.

In the application of a UV radiation curable material as a subunit orcommon matrix, light intensity and cure time are factors by which theresultant modulus of the film can be controlled. The light dose, i.e.,the radiant energy arriving at a surface per unit area, is inverselyproportional to line speed, i.e., the speed the radiation curablematerial moves under a radiation source. The light dose is the integralof radiated power as a function of time. In other words, all else beingequal, the faster the line speed the higher the radiation intensity mustbe to achieve adequate curing. After a radiation curable material hasbeen fully irradiated, the material is said to be cured. Curing occursin the radiation curable material from the side facing the radiationsource down or away from the source. Because portions of the materialcloser to the light source can block light from reaching non-curedportions of the material, a cure gradient may be established. Dependingon the amount of incident light, a cured material may therefore exhibitdifferent degrees of cure, and the degrees of cure in a film can havedistinct modulus characteristics associated therewith.

Thus the degree of cure affects the mechanical characteristics throughthe cross link density of the material. For example, a significantlycured material may be defined as one with a high cross link density forthat material, and may, for example, be too brittle. Further, anundercured material may be defined as one having a low cross linkdensity, and may be too soft, possibly causing an undesirable level ofribbon friction.

Optical fiber ribbons with subunits and a common matrix with generalmodulus characteristics may define a backdrop for the present invention.For example, EP-A-856761 discloses a ribbon having a common matrixsurrounding discrete single-fiber optical subunits each including arespective subunit matrix. Each subunit matrix includes six tensionwires formed of aramid fiber, glass fiber, or steel. The modulus of thecommon matrix can be set lower than that of the subunit matrix. Thisdesign is disadvantageous because the tension wires are expensive, addthickness and stiffness to the ribbon as a whole, and can presentsignificant manufacturing difficulties. Moreover, single-fiber subunitshave limited transmission capabilities.

In addition to surrounding single-fiber subunits, the common matrix canhave a high modulus thereby defining a relatively rigid protective outerlayer. For example, EP-A-843187 discloses a ribbon having a multi-layercommon matrix with an outer protective layer. The layers of the commonmatrix have differing rigidness characteristics. The common matrix canhave a modulus of 5 to 100 kg/mm², and the subunit resin layer can bethe same material as the common matrix. A rigid outer layer is alsodiscussed in an International Wire & Cable Symposium paper entitled“ANALYSIS OF A MODULAR 24-FIBER RIBBON FOR THE DISTRIBUTION NETWORK”(1998). The ribbon discussed therein includes a pair of subunitssurrounded by a common matrix. The common matrix is more rigid than thesubunit matrix for strengthening the structure of the ribbon. Inaddition, protective matrix layers with a relatively high modulus aredisclosed in JP-A-80-62466 and JP-A-91-13773.

Moreover, the common matrix can exhibit predefined frictioncharacteristics. For example, EP-A-822432 discloses a pair of subunitssurrounded by a common matrix including a base resin material having afunctional group of low compatibility dispersed therein. The functionalgroup forms discrete domains of about 5 microns in diameter in thecommon matrix. The domains have a low modulus relative to the base resinof the common matrix for lowering the coefficient of friction (COF) ofthe common matrix. Another example of a COF effect is disclosed in U.S.Pat. No. 5,524,164, wherein part of the optical fiber ribbon includes acomponent of poor compatibility forming a discontinuous phase having alow modulus in the outer resin layer surrounding a pair of subunits. Thecomponent of poor compatibility is intended to migrate to the ribbonouter surface for reducing sliding friction.

Object(s) of the Invention

It is an object of the present invention to provide an optical fiberarray having: at least one subunit including at least one optical fibertherein surrounded by a respective subunit matrix having a subunitmatrix modulus; a common matrix disposed adjacent to the at least onesubunit having a common matrix modulus; a subunit/common matrix modulusratio being defined as a ratio of the subunit matrix modulus withrespect to the common matrix modulus; the subunit/common matrix modulusratio being about 1.5:1 or more.

It is an object of the present invention to provide an optical fiberarray having at least one subunit including at least two optical fiberstherein surrounded by a respective subunit matrix having a subunitmatrix modulus; a common matrix disposed adjacent to the at least onesubunit having a common matrix modulus; the subunit matrix modulus beingunequal to the common matrix modulus whereby the common matrix is lessrigid than the subunit matrix.

It is an object of the present invention to provide an optical fiberarray an optical fiber array having:

at least one optical fiber ribbon with at least two optical fiberstherein surrounded by a respective first matrix having a subunit matrixmodulus;

an second matrix disposed adjacent to the at least one subunit having amatrix modulus;

the subunit matrix modulus being unequal to the second matrix moduluswhereby the second matrix is less rigid than the first matrix.

It is an object of the present invention to provide an optical fiberarray having: at least one subunit including at least one optical fibertherein surrounded by a respective subunit matrix; a common matrixdisposed adjacent to the at least one subunit; an adhesion zone defininga controlled adhesion bond between the common and subunit matrices thatis robust enough to inhibit inadvertent separation of the subunits butis weak enough to avoid breakage of the subunit matrix during subunitseparation.

It is an object of the present invention to provide an optical fiberarray having: at least one subunit including at least one optical fibertherein surrounded by a respective subunit matrix having a subunitmatrix modulus; a common matrix disposed adjacent to the at least onesubunit is having a common matrix modulus; a subunit/common matrixmodulus ratio being defined as a ratio of the subunit matrix moduluswith respect to the common matrix modulus; the subunit/common matrixmodulus ratio being greater than about 1.5:1; and an adhesion zonedefining a controlled adhesion bond between the common and subunitmatrices.

It is an object of the present invention to provide a method ofmanufacturing an optical fiber array comprising the steps of:

(a) supplying at least one subunit including at least one optical fibertherein surrounded by a respective subunit matrix;

(b) creating a common matrix adjacent to the at least one subunit andcuring the common matrix so that a common matrix modulus of the commonmatrix is less than a subunit matrix modulus of the subunit matrix; and

(c) prior to and during curing of the common matrix, defining anadhesion zone between the common and subunit matrices that is robustenough to inhibit inadvertent separation of the subunit but is weakenough to minimize breakage of the subunit matrix during subunitseparation.

The step of defining the adhesion zone can include oxidizing an outersurface of the subunit matrix. The oxidation can be accomplished byCorona treatment of the subunit matrix. In addition, the step ofdefining the adhesion zone can include reacting the common matrix withpolar groups made by an oxidation of the outer surface of the at leastone subunit. Moreover, the step of defining the adhesion zone caninclude applying and curing a bonding treatment, and subsequentapplication and curing of the common matrix. Further, the step ofdefining the adhesion zone can include, in combination, the steps ofoxidizing an outer surface of the subunit and applying a bondingtreatment thereto.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURES

FIG. 1 is a cross sectional view of an optical fiber ribbon according tothe background of the present invention.

FIG. 2 is a cross sectional view of an optical fiber ribbon according tothe present invention.

FIG. 2a is an enlarged partial view of the optical fiber of FIG 2.

FIG. 3 is a cross sectional view of an optical fiber ribbon according tothe present invention.

FIG. 3a is an enlarged partial view of the optical fiber of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

The concepts of the present invention can be used to manufacture arraysof optical fibers arranged together, for example, generally planaroptical fiber ribbons 20,40 (FIGS. 2-3). Key features of optical fiberribbons made according to the present invention comprise the adhesion ofthe common matrix to the subunits, and/or the Young's moduluscharacteristics of the subunit and common matrices. Optical ribbons20,40 are robust to cable processing, and include a low attenuationafter cabling operations. In addition, optical ribbons 20,40 are robustto handling by the craft, including consistent separability by hand ortool into optical fiber sub-units and the avoidance of stray fibers orwings.

Each optical fiber ribbon 20,40 includes respective optical fibers 22. Atypical optical fiber 22 includes a silica-based core that is operativeto transmit light and is surrounded by a silica-based cladding having alower index of refraction than the core. A soft primary coatingsurrounds the cladding, and a relatively rigid secondary coatingsurrounds the primary coating. Optical fibers can be, for example,single mode or multi-mode optical fibers made commercially available byCorning Incorporated.

Optical fiber ribbons 20,40 include respective subunits 26,46 eachhaving respective subunit matrix layers 23,43 in which optical fibers 22are disposed. A common matrix 24 surrounds each subunit 26 (FIG. 2), anda common matrix 44 is interposed between facing sides of subunits 46(FIG. 3). As further described below, adhesion zones 28,48 arerespectively defined between respective subunit and common matrices23,24 and 43,44 (shown schematically in FIGS. 2A,3A).

In general, subunits 26,46 can be made by arranging optical fibers 22generally in parallel and extruding a UV curable, subunit matrixmaterial therearound and curing it with a UV radiation source. Next, aUV curable common matrix 24 is extruded around and circumscribessubunits 26 thereby defining optical fiber ribbon 20. A UV curablecommon matrix 44 can be applied to facing sides of subunits 46 therebydefining optical fiber ribbon 40. In either event, common matrices 24,44can be cured with a UV radiation source. The UV radiation source may bean H or a D bulb: an H bulb is preferred for establishing a curegradient and better peelability, and a D bulb is preferred where it isdesired to have minimum cure gradient. In a preferred embodiment, therespective formulations of common matrices 24,44 may comprise a UVcurable acrylate material including a photoinitiator. Alternatively,common matrices 24,44 can include a photoinitiator having a photoactivepeak absorbance in the relatively long wavelength UV spectrum. Forexample, common matrix layers 24,44 can include a one or morephotoinitiators having an alpha-hydroxy-ketone material and a phenylphosphine oxide derivative, for example, DAROCURE 4265 (HMPP/TPO)(270-290 nm), made commercially available by Ciba, or another suitablephotointiator. Additionally, for enhancing strippabilty/peelability ofsubunit matrix 23,43 with respect to optical fibers 22, optical fiberribbons 20,40 may include respective release layers (not shown) betweenoptical fibers 22 and respective subunit matrices 23,43, for example asdisclosed in U.S. Pat No. 4,900,126, which is hereby incorporated byreference herein in its entirety.

According to the present invention, the respective thicknesses of commonmatrices 24,44 are minimized to increase the adhesion of the commonmatrix to the subunit matrix, and to decrease the cohesive strength ofthe common matrix relative to the subunit matrix. The thickness t (FIG.2) of common matrix 24 is up to about 25 μm with a preferred range ofabout 5 μm to 10 μm, as disposed over a subunit thickness of about 2 μmto about 75 μm or more.

Optical fiber ribbons made in accordance with the present invention willhave a controlled subunit/common matrix modulus ratio. Thesubunit/common matrix modulus ratio is accomplished by selectingsuitable UV curable materials and controlling the UV radiation that theyare exposed to in the curing process so that the desired moduluscharacteristics are attained. Preferably, the modulus characteristics ofeach cured matrix are unequal. In other words, the common matrices 24,44are less rigid than respective subunit matrices 23,43. Morespecifically, UV curable materials, radiation sources, and processparameters are selected so that the subunit/common matrix modulus ratiois in the range of about 1.5:1 to about 60:1. The subunit/common matrixmodulus ratio can be defined as a ratio of the subunit matrix moduluswith respect to the common matrix modulus. More preferably, thesubunit/common matrix modulus ratio is in the range of about 2.3:1 toabout 25:1. Most preferably, the subunit/common matrix modulus ratio isin the range of about 18:1, i.e., about 900 MPa:50 MPa. The foregoingranges assure that the cohesive strength between common matrices 24,44and respective subunit matrices 23,43 is such that during a subunitseparation procedure the common matrix should fail prior to fracture ofthe subunit matrix.

In addition to modulus characteristics, common matrices 24,44 exhibitgood friction characteristics. A suitable UV curable material minimizesthe static COF (μ_(static)) of the common matrix in order to reducestress induced attenuation caused by subunit separation with a tool. Theoptimal μ_(static) range is less than or equal to about 1.0. Further,ribbon matrices 23,43 can include an additive for reducing COF, such asis disclosed in commonly assigned U.S. Pat. No. 5,561,730, which isincorporated by reference herein in its entirety. U.S. Pat. No.5,561,730 also discloses a suitable method for determining the value ofμ_(static).

Several methods according to the present invention can be used to defineadhesion zones 28,48, shown schematically in FIGS. 2A,3A, betweensubunit matrices 23,43 and respective common matrices 24,44. Forexample, on a molecular level, adhesion zones 28,48 can be formed byoxidation of the outer surfaces of subunit matrices 23,43 and subsequentapplication and curing of common matrices 24,44. Alternatively, adhesionzones 28,48 can be formed by application of a bonding treatment andsubsequent application and curing of common matrices 24,44. The functionof adhesion zones 28,48 is to establish a controlled adhesion betweenthe common and subunit matrices that is robust enough to inhibitinadvertent separation and the formation of wings during subunitseparation. On the other hand, the controlled adhesion is delimited soas to avoid breakage of any subunit matrix during subunit separation,thereby avoiding the formation of stray fibers.

A Corona discharge treatment can be applied to the surface of subunits26,46. The present invention contemplates the use of a conventionalCorona treatment device in forming adhesion zones 28,48. The Coronatreatment can include a process whereby subunits 26,46 are, after curingby UV radiation, passed over a grounded conductor. A high voltageelectrode is located above the conductor and is spaced so as to leave asmall air gap between the subunits and the electrode. The Coronadischarge oxidizes the matrix material and forms polar groups/reactivesites on the subunit matrix material. The common matrices 24,44 bondwith the reactive sites during application and UV curing thereof.Adhesion zones 28,48 comprise the bond layer of the oxidized outersurface of subunits 26,46 with respective reactive sites on commonmatrices 24,44.

Adhesion zones 28,48 can also comprise a bonding treatment includingphotoinitiators and/or monomers that are diluted or taken into solutionwith a solvent. The bonding treatment is applied to subunits 26,46 in avery thin, evenly distributed layer. The bonding treatment can be a UVacrylate material combined with a photoinitiator. Preferably thephotoinitiator has a high absorption rating of approximately 250 nm forhigh energy activation with an H-bulb, e.g., an alpha-hydroxy ketonematerial, for example DAROCURE 1173 (HMPP), IRGACURE 184 (HCPK) withbenzophenone derivatives, or IRGACURE 500 (HCPK/BP) made commerciallyavailable by Ciba. Once the photoinitiator is activated, it combineswith respective unreacted sites in subunit matrices 23,43 and makes thesites reactive. Common matrices 24,44 are then respectively appliedthereover and irradiated with common matrices 24,44 upon irradiationwith a UV light source.

Alternatively, the bonding treatment can comprise a monomer, forexample, a 2-(Ethoxyethoxy) Ethyl Acrylate with DipentaerythritolPentaacrylate, that is taken into solution with a solvent, e.g.,acetone, or a non-flammable solvent. This monomer-based bondingtreatment can be operative to permeate the subunit matrix material andgain a good molecular grip thereinto. The monomer-based bondingtreatment also provides a site for reacting with the common matrixmaterial 24,44. In addition, the bonding treatment can be a mixture of aphotoinitiator and a monomer taken into a common solution.

The bonding treatment can be applied with a die, wiped on, applied as amist, or applied by any other appropriate method onto subunits 26,46.The bonding treatment can be partially or completely cured with a UVlight source prior to application of the common matrix. Preferably thebonding treatment forms a thickness of about 5 μm or less. The bondingtreatment can be applied in-line with application of the common matrixmaterial; however, it is contemplated that the bonding treatment can beapplied in an off-line process as well.

To enhance the absorbance of common matrices 24,44, subunit matrices23,43, and/or the bonding treatment, the formulations thereof mayinclude at least one conventional UV absorber additive. UV absorbers actby absorbing incident light and converting it to heat energy. The use ofa UV absorber, however, may reduce cure speed of the formulation—tocounter this, the addition or increased concentration of photoinitiatorin the formulation may be appropriate. Suitable UV absorbers aredisclosed in U.S. Pat. No. 4,482,224, which is incorporated by referenceherein. Another suitable UV absorber is sold under the trade nameTINUVIN, made commercially available by Ciba.

In view of the foregoing and in general, a method of manufacturing anoptical fiber array can comprise the steps of:

(a) supplying at least one subunit including at least one optical fibertherein surrounded by a respective subunit matrix;

(b) creating a common matrix adjacent to the at least one subunit andcuring the common matrix so that a common matrix modulus of the commonmatrix is less than a subunit matrix modulus of the subunit matrix; and

(c) prior to and during formation of the common matrix, defining anadhesion zone between the common and subunit matrices that is robustenough to inhibit inadvertent separation of the subunit but is weakenough to minimize breakage of the subunit matrix during subunitseparation.

The step of defining the adhesion zone can include oxidizing an outersurface of the subunit matrix. The oxidation can be accomplished byCorona treatment of the subunit matrix. The step of defining theadhesion zone can include reacting the common matrix with polar groupsmade by an oxidation of the outer surface of the at least one subunit.In addition, the step of defining the adhesion zone can include applyingand curing a bonding treatment, and subsequent application and curing ofthe common matrix. The step of defining the adhesion zone can include,in combination, the steps of oxidizing an outer surface of the subunitand applying a bonding treatment thereto.

The present invention has thus been described with reference to theforegoing embodiments, which embodiments are intended to be illustrativeof the inventive concepts rather than limiting. Skilled artisans willappreciate that variations and modifications of the foregoingembodiments may be made without departing from the scope of the appendedclaims. For example, the inventive concepts can encompass non-planaroptical fiber arrays, for example, a low modulus matrix in a cylindersuch as a blown fiber subunit. Additionally, the optical fiber array canbe, for example, a bundle of optical fibers connected by a subunitmatrix and surrounded by a common matrix according to the presentinvention. In another contemplated variation, UV curable acrylates canbe replaced by thermoplastics including, for example, PVC, PE, SEBS,and/or PP. The present inventive concepts can be used in the formationof ribbon stacks so that two or more optical fiber ribbons in a stackare bonded together with a low modulus matrix material. Additionally,the concepts of the present invention are applicable to multi-coreoptical fibers.

Further, optical fiber ribbons can be prepared having subunits with anynumber of optical fibers therein, for example, one to thirty-six opticalfibers or more. An optical fiber array (not shown) can be preparedhaving at least one optical fiber ribbon with at least two opticalfibers therein surrounded by a respective first matrix having a subunitmatrix modulus; a second matrix disposed adjacent to the at least onesubunit having a matrix modulus; the subunit matrix modulus beingunequal to the second matrix modulus whereby the second matrix is lessrigid than the first matrix. Moreover, oxidation of the subunit outersurface can be accomplished with a flame treatment or exposure to UVradiation. Further, adhesion zones 28,48 can be formed by a combinationof oxidation of the subunit surfaces and application of a bondingtreatment.

Accordingly, what is claimed is:
 1. An optical fiber array comprising:at least one subunit including at least one optical fiber therein, saidoptical fiber comprising an inner layer and a relatively rigid outerlayer, said outer layer being surrounded by a respective subunit matrixhaving a subunit matrix modulus; a common matrix disposed adjacent tothe at least one subunit having a common matrix modulus, said subunitmatrix being at least partially disposed between said optical fiberouter layer and said common matrix; a subunit/common matrix modulusratio being defined as a ratio of the subunit matrix modulus withrespect to the common matrix modulus so that the common matrix isrelatively less rigid than said subunit matrix; the subunit/commonmatrix modulus ratio being about 1.5:1 or more.
 2. The optical fibergroup of claim 1, a thickness of the subunit matrix being about 2 μm toabout 75 μm or more.
 3. The optical fiber group of claim 1, a thicknessof the common matrix being about 5 to about 25 μm or more.
 4. Theoptical fiber group of claim 1, the subunit/common matrix modulus ratiobeing about 2.3:1 to about 25:1.
 5. The optical fiber group of claim 1,the common matrix having a COF range of about μ_(static) less than orequal to about 1.0.
 6. The optical fiber group of claim 1, the opticalfiber array comprising a generally planar structure.
 7. The opticalfiber group of claim 1, the subunit/common matrix modulus ratio beingabout 60:1 or less.
 8. An optical fiber array comprising: at least onesubunit including at least two optical fibers therein, said opticalfibers comprising respective inner layers and relatively rigid outerlayers, said outer layers being surrounded by a respective subunitmatrix having a subunit matrix modulus; a common matrix disposedadjacent to and at least partially covering the at least one subunit,said common matrix having a common matrix modulus, said subunit matrixbeing at least partially disposed between said optical fiber outerlayers and said common matrix; the subunit matrix modulus being unequalto the common matrix modulus, said common matrix modulus being lessrigid than the subunit matrix modulus.
 9. An optical fiber arraycomprising: at least one optical fiber ribbon with at least two opticalfibers therein, said optical fiber comprising an inner layer and arelatively rigid outer layer, said outer layer being surrounded by arespective first matrix having a subunit matrix modulus; a second matrixdisposed adjacent to and at least partially covering the at least onesubunit having a second matrix modulus, said first matrix being at leastpartially disposed between said optical fiber outer layer and saidcommon matrix; the subunit matrix modulus being unequal to the secondmatrix modulus whereby the second matrix is less rigid than the firstmatrix.
 10. An optical fiber array comprising: at least two opticalfiber subunits each respectively including a plurality of optical fibersarranged in a generally planar array therein, said optical fiberscomprising an inner layer and a relatively rigid outer layer, said outerlayers being surrounded by respective subunit matrices having a subunitmatrix modulus; a common matrix disposed adjacent to the subunitmatrices and having a common matrix modulus, said subunit matrices beingat least partially disposed between said optical fiber outer layer andsaid common matrix; a subunit/common matrix modulus ratio being definedas a ratio of the subunit matrix modulus with respect to the commonmatrix modulus so that the common matrix is relatively less rigid thansaid subunit matrices; the subunit/common matrix modulus ratio beingabout 1.5:1 or more.